Pressure welding electrode



SePt- 20 1932. M. M. AusnN i 1,878,095

PRESSURE WELDING ELECTRODE Filed Jan. 17, 1929 coPPER wl RE\ JM FINE TUNGSTEN l Patented 20, 1932 Y UNITED STATES ,i vLuana;

PATENT .OFFICE -MINEB H. AUSTIN, OF XWAUXEGAN, ILLINOIS, ASSIGNOB TO FAN STEEL PRODUCTS OOI- PANY, INC., OFNORTH CHICAGO, ILLINOIS, A CORPORATION OF NEW YORK PRESSURE WELDING ELECTBODE Application mea Ianary 17, 192s. serial Nassau,

hardness than electrodes heretofore used, and

which will have a longer life.

A further object is to provide an improved process for making electrodes of this type.

A further object is to provide a composition 2 of matter consisting of compacted tungsten particles, all of the voids between said particles being filled with the metallic copper.

A further object is to provide a process for making electrodes of this ty e which will avoid the necessity of usin igh pressures and which avoids the step o sintering.

A further object is to avoid sinterlng and intermolecular reactions thereby preserving extremely finely divided tun sten particles in the finished product, thus o taining greater resulting hardness for a given tungsten content. l

Other objects will be apparent as the detailed description of my invention proceeds.

My invention may be briefly characterized Yas follows:

Chemically pure tungsten powder is tamped in a graphite crucible, the crucible is inserted in an electric furnace surrounded by an atmosphere of hydrogen, the temperaturel is raised to a pointslightly above the melting point of copper, and copper wire isslowly and` gradually fed into the compacted tungsten mass so that copper is adually absorbed and drawn into the mass o tungsten particles due to the effect of gravity, capillary attraction and surface tension.

-I have discovered that when extremely finely divided tungsten powder is saturated with copper in the mannerjdescribed an electrode is i roduced whichv combines the strength, rlgidity and refractory properties of tungsten with the conductivity of co per.

fp copvI believe that the product is a mixture o per and tungsten and that there is no chemical reaction or solution such as takes place, for instance, when copper and aluminum are treated in this'manner. Apparentl each metal maintains its own identity an is in the iinal electrode as such.

The copper is materially hardened by this treatment, however, and I believe that the hardness is increased with the decrease in the size of tungsten particles. The failure ofl copper under compression is due to the slidrng of copper molecules which are apparently 1n parallel planes. By introducin particles of tungsten in the mass of copper this sliding is prevented, especially when the tungsten particles are of microscopic size.

If large particles of tungsten are used in this electrode the tungsten particles must be sintered or fritted together to give the necessary strength because otherwise copper will slide around the particles. When microscopic particles of tungsten are, used for this purpose they t in the interstices of the copper so that the electrode is essentiall -a matrix ofcopper stiffened by finely divi ed par- ,ticles of tungsten, the function of which is to prevent the copper molecules from sliding over each other.

Tungsten is a fairly good conductor and, as

above pointed out, tungsten does not lower the conductivity of copper in my improved electrode, but supplements it.

In the accompanying drawin in which I have shown a preferred embodiment of my invention and in which similar parts are represented by like reference characters,

Fig. l is a diagrammatic section through my furnace showing the means for supplying copper to the heated tungsten owder; and

Fig. 2 is a section of my weldlng electrode composition a'srit is removed from the crucible.

Finely divided pared by reducing chemically pure tungsten oxide with hydrogen, and it is essential that the tungsten be free from impurities and that` tungsten powder 10 is pre-- 'it be in extremely finely divided form each it cuses such a shrinkage that a thin la er particle being in reality a plurality of particles of submisci'oscopic dimensions.

Finely divi'dedtungsten powder prepared I in this manner is poured into a raphite crucible 11 and compactedby sha 'ng manually tamping it'wlth a pestle..

The graphite crucible 11 may-be of anyy size or shape, and it is referably formed to the shape of the inishe product Vto minimize the necessity for workin or tooling. h

While I have describe a graphite crucible, it is understood that this is illustrative onl and that any suitable inert .material whic l5 will withstand the working temperature may be utilized for this purpose.

The crucible 11 is inserted in an electric furnace 12 vwhichmay be brieiiy described as a. porous alundum cylinder 13 with an 20 alundum disc14 for the bottom. This refractory' cylinder is Asurrounded by resistance coils of molybdenum wire 15 connected to power supply by conductorsvl and 17.

The .transformer and means for regulating the current form vno partof the present invention and are not, therefore, shown in the drawing. Y Y l The 'molybdenum' wound alundum cylinder is inserted in magnesia 18 or other refractory powder containedV in a cast ironbox 19. It is understood that all of these'materials density and hardness ofthe final product is '45 somewhat dependent upon the amount of tamping). Whenthe ,temperatureof the tungsten powder lreaches a point slightly above the melting point of copper, a wire 24 of chemically pure electrolyticcopperis applied to the surface of the tungsten mass where it melts and 'soaks' into Athe powder like water would soak into sand, wetting all of the particles and filling all the voids between them. The'copperis added -until an excess ture isallowe'd to cool. f Y- Y The resulting material .may be easily removed from the graphite moldY because the copper tungsten electrode shrinks slightly on 00 cooling. This is due tothe e'iz'ectV of the copper on the tungsten because 'if no copper were 55 remains at the surface, after which themixaddedf the tungsten 'wouldfnot -shrink and.

could not be removed from the mold. The

copper not only causes sulicient shrinkage to remove the electrode from the crucible, but l Y fore the electrode is subjecte to use. it or by is, in fact, detrimental because 'it tends'to' more than the finely divided pure chromium pow er.,

ly above the melting point of copper.

of copper is formed on all sides of the e ectrode, as shown in Fig. 2. This copper surface can be easily removedb machining be- The percent of copper andtungsten will 7 depend upon the degree to which the .tungsten particles are compacted. In no case is Y f great pressure required, and vgreat pressure create large particles of tungsten and to pre- 'u vent' the copper from penetrating through-v outY the mass. vOrdinarily I compact the' powder by gently tamping it with a pestle so that the voids are filledl with about 35% eo per by weiglht (Y hich would be considera iy alf by volume). While I have described a welding electrode.. Y in which tungstenpowder is saturated with copper, or, in other words, in whichthe copper is hardened by microscopic particles of tungsten, itis understood that this is only ile 'Ycan be obtained in Yinely divi ed powder suitable for my purpose. Chromium is ad'- niirable because of its high conductivity, the only diiculty 'being the step of pre aring Copper'is illustrative only, as I contemplate that silver and other. conductors may be used, as will be apparent to any one skilled intheart. i

Attention is particularly directed to the factthat I'avoid the use of high pressures and high temperaturesl throughout the whole process. i f

The temperature has been defined as sli ht` t is usually'between 1150 degrees and 1200 deees C., the lower temperatures bein satis-l A actory when the powder is suicient y line.

The theorywhich .I have set forth :to ex-A plain the phenomenal leffect of finely divided tungsten on copper is given merely to aid in .theunderstanding of my invention, but `I d0 not limit myself-to this or any other theory, v :my process being clearly de ned by thev physical steps described. Y v4I ll While I have described a preferred embodiment of my invention, it is understoodthat I amnot limited `to the details therein set forth except as defined by the following claims. f

Iclaimif.` .v i'

1. A welding 'electrode comprising in the nal f composition from 25% to A45% by weight of copper andYmicroscopic tungsten particlesmaking -up the remainder and dis-v persed throughout the copper to prevent .in-v termolecular slippage of the copper.

2. A welding electrode of tungstenand copper in which the tungsten is inthe form 'm Lemon of finely divided particles making up at least 65% by weight of the electrode.

3. A welding electrode of unsintered tungsten and copper in which the cop r makes up from 25 to 45% of the whole an the tungsten is in the form of slip-interfering particles dispersed throughout the copper.

In witness whereof,.I hereunto subscribe my name this 14th da of January, 1929.

MIER M. AUSTIN. 

